The variation in density and biomass of earthworms with physical and chemical properties of soil after forest land-use change

The earthwormis considered as one of the most important ecological indicators in assessing the soil quality of the soil ecosystems. The aim of this research was the investigation of forest land-use changes on the earthworm’s density and biomass related to the soil properties. For this purpose, 40 soil profile and earthworm samples were randomly taken from 0-25 cm in four different land-uses (Less-disturbed forest, disturbed forest, agricultural irrigated land (Medicago sativa) and orchard (Pyrus sp. and Malus sp.) in Baneh county forest's, Kurdistan province. The results showed that soil organic matter in different land uses decreased in all land uses compared to the less-disturbed (SOM=2.95 percent) forest. The disturbed forest dedicated the least amount of phosphorus and electrical conductivity than the other land uses. There were significant differences among other soil factors including nitrogen, C/N, potassium, pH, moisture, and gravel percent. In addition, the most and the least density of earthworms were belonged to the less-disturbed forest (204.8/m-3) and disturbed forest (44.8/m3), respectively. In general, the density of earthworms showed a positive significant correlation with their biomass as well as canopy percent and negative significant correlation with gravel and the soil rock percent. Increasing of earthworm’s biomass showed a positive significant correlation with the soil organic matter, nitrogen and moisture percent, and negative significant correlation with soil rock percent. As a conclusion, forest land-use changing and forest utilization have reduced the density of earthworms, which was decreased significantly in the disturbed forest and agricultural irrigated land compared to less-disturbed forest.